1. Field of the Invention
The present invention relates to azo compounds useful in the dyeing of polyolefins. More particularly, the invention relates to azo compounds having a benzthiazolyl group and which have utility in the dyeing of metallized, or metal-containing polyolefin, especially nickel-containing polypropylene textile materials.
2. Description of the Prior Art
Polypropylene, because of its excellent mechanical strength, high elasticity and resistance to solvents, has found increased utility in recent years as filaments, yarns, fabrics, ropes and the like. Commercially available polypropylene materials generally contain metals or metal salts or chelates to provide stability against degradation due to light. These metals or metal salts or chelates also serve to provide reactive sites for dyes.
Dyes, more particularly, chelatable dyes, having specific utility in the dyeing of such metal-containing, or metal-modified, polypropylene are reported extensively in the literature. Chelatable azo dyes disclosed for use in dyeing metallized polyolefin commonly contain o,o'-dihydroxyazo; o-hydroxy-o'-carboxyazo; o-hydroxy-o'-aminoazo; or o-carboxy-o'-aminoazo chelatable groups. Certain azomethine structures similarly substituted ortho to the --C.dbd.N-- link have also been reported.
Thus, for example, Siegrist et al, U.S. Pat. No. 3,399,027, discloses a process for dyeing polyolefins containing organic nickel chelate complexes with an aqueous dispersion of an azomethine dye. As the azomethine dyes there are disclosed dyes of the formulas: ##STR2## where
X is OH or COOH, and
Y is phenylazo or naphthylazo.
Mohr et al, U.S. Pat. No. 3,389,956, discloses the dyeing of nickel-modified polypropylene textiles with an acyl-o,o' -dihydroxyazo or acyl-o-hydroxy-o'-carboxyazo dye of the formula: ##STR3## Y being hydroxy or carboxy.
Dyes having chelatable groups of the o,o'-dihydroxyazo and o-hydroxy-o'-carboxyazo type, however, do not produce acceptable shades on metallized polypropylene. Although these groups apparently bind strongly to the metal compound contained in the polypropylene and give dyeings having excellent fastness to rubbing, washing and dry cleaning, they tend to produce dull and rather weak colors. These dyes are also disadvantageous in that there is a drastic change in hue between the unchelated and chelated dyes which can cause uneveness on the metallized fiber depending on the concentration of metal throughout the fiber. This difference in hue between chelated and unchelated dyes may also cause differences in hue between the dyed pile of a carpet of a metal-containing polypropylene and the carpet backing, which is usually made from non-chelatable materials.
It is an object of the present invention, therefore, to provide dyes suitable for dyeing metal-containing, or metal-modified, polyolefins, and particularly, polypropylene, and which avoid or minimize the problems associated with the dyes heretofore employed in the art.
This and other objects of the invention will become apparent from the following summary and description of preferred embodiments.